1. Field of the Invention
The present invention relates to a terminal fitting for connection to a flat conductor.
2. Description of the Related Art
Prior art flat conductors include an FFC (flexible flat cable) and an FPC (flexible print circuit board). The prior art FFC includes a plurality of parallel conductive paths sandwiched between insulation sheets, such that the FFC resembles a flexible ribbon. Terminal fittings are connected to the respective conductive paths of the FFC by embedding the conductive paths in the insulation sheet or by tearing off the insulation sheet on a section of the FFC to expose sections of the conductive paths on one surface of the FFC.
The former method is called a through type method, and has an advantage of omitting the stage of tearing off the insulation sheet. This method is disclosed in Japanese Patent Application Laid-Open No. 50-100585, and is shown in FIG. 7. In this method, contact blades 3 are erected on both side edges of a base plate 2 of a terminal fitting 1. Both contact blades 3 pierce a conductive path 5 of an FFC 4 to bring cut end surfaces of the conductive path 5 into the contact blade 3.
However, in this method, there is a fear that when the contact blade 3 is pierced into the conductive path 5, the FFC 4 floats between the contact blades 3 and thus the cut end surfaces of the conductive path 4 do not contact the contact blade 3 favorably. To avoid the unfavorable contact, it is conceivable to press the FFC 4 when the contact blade 3 is pierced into the conductive path 5.
As shown in FIG. 8, the contact blades 3 project outward from the side edges of the base plate 2. The space between the left and right contact blades 3 must be small if the conductive path 5 is narrow. In this situation, the width y of the base plate 2 must be very narrow, as shown in FIG. 8A. Thus, the base plate 2 has a low degree of strength. To improve the strength of the base plate 2 without changing the interval between the left and right contact blades 3, it is absolutely necessary to make a channel-type base plate having a side wall erected on both sides of the base plate to secure a large width x. The contact blades 3 then are erected on the upper edge of side wall 2A such that the contact blades are flush with the side wall 2A, as shown in FIG. 9.
The construction in which the contact blades 3 are flush with the side wall 2A requires the FFC 4 to be pressed toward the base plate 2 so that the contact blades 3 pierce into the conductive path 5. However, as shown in FIG. 10, this design causes the upper edge of the side wall 2A to catch the FFC 4. As a result, the FFC 4 cannot be pressed to the bottom of the base plate 2. That is, a flank 8 is formed between the FFC 4 and the bottom of the base plate 2. As a result, the FFC 4 flexes and escapes to the flank 8. In this case, a sufficient contact pressure may not be obtained between a cut surface 5A of the conductive path 5 and the contact blades 3 or only a part of an insulation sheet 6 is in contact with the surface of the side wall 2A of the contact blade 2. Thus, there is a possibility that the connection method is not reliable in electrical contact.
The present invention has been completed in view of the above-described situation. Thus, it is an object of the present invention to allow a reliable contact between a contact blade of a terminal fitting of through type and a cut surface of a conductive path of a flat conductor.